Is A Transition Metal-Silicon Quadruple Bond Viable?

Quadruple bonding in heavier main group elements is not known albeit having four valence orbitals accessible for bonding. Here we report the unprecedented quadruple bonding between a silicon atom and a transition metal fragment in the (1)A(1) electronic ground state of C-3v symmetric SiRu(CO)(3) based on high level theoretical calculations. Various bonding analyses reveal the nature of the Si(sic)Ru quadruple bonding interaction, which involves one usual Si-Ru sigma bond, two usual Si-Ru pi bonds and one additional Si -> Ru dative sigma bond.